I would consider it too, if I was a different age, but to buy it now (almost 48) means that I would really only need it for 2 years because I can get a retirement visa at 50.
I've searched online for this before and there's a few threads on forum.thaivisa.com, though some are a few years old. One from 2017, says, "I went to a local pharmacy, and they had Welbuitrn XL in 150 mg and 300 mg for 1,00 and 1550 respectively," and from 2016, "No generic available. Available only as Wellbutrin XL and Quomem, both imports"
I’m Canadian too and going next week without a visa (visa exempt). Can stay up to 45 days. Plus a 30 day extension if you want. But I do have the COE. As long as you follow the COE instructions, you’re good: